Measuring instrument for gear-wheel teeth



Aug. 24 1926. 1,597,636

w. E. S'YKES MEASURING INSTRUMENT FOR GEAR WHEEL TEETH Filed August 9, 1921 3 Sheets-Sheet 1 9 m, Mk

Aug. 24,1926. 1,597,636

' W. E. SYKES MEASURING INSTRUMENT FOR GEAR WHEEL TEETH Filed August 9, 1921 3 Sheets-Sheet 2 W' illz'am av I e llbi'iz'qs'.

Aug. 24, 1926. 1,597,636

' W. E. SYKES MEASURING INSTRUMENT FOR GEAR WHEEL TEETH Filed August 9. 1921 3'Sheets-Sheet 5 l Patent e'dAug. 24,; 1 926. j I j UNITED STATES PATENT QFFICE.

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EEASUBING INSTRUMENT FOR GEAR-WHEEL TEETH.

- Application flled Augj-iist 9,1 aai, Serial No. 490,978, and in Great Britain September 20, 1920.

For meas'u ring the thickness of gear wheel teeth instruments having a vernier scale are generally used, but in certaln'classes of precision work' more precise readings are required. The object of the present invention is to provide an instrument whereby more precise measurements maybe made with equal or greater facility than is possible by means of a vernier gauge.

According to the present invention I pro vide a form of caliper gauge consisting of a beam on which are mounted two aws. One or both jaws, is or are arranged slidable and adjustable in such a manner that the distance of the inside faces may be varied to suit teeth of various pitches. The inside faces of the said jaws are arranged at an angle to each other. I n

I'further mount on the aforementioned beam a test indicator which maybe of any,

. known or convenient'form,- but I prefer to employ the type having a circular 'dial known as a dial test indicator. The test indicator is mounted on the beam in a manner that the plunger or contact spindlemay operate between the inside angular faces ofthe jaws, and by this arrangement the contact point of the indicator is'adapted to make contact with the top of the tooth being Fig. 2 an end elevation.

measured when the inside angular faces of the jaws. make contact with the sides or flanks of the same tooth.

In order to obtain measurements with the instrument made as already described it is necessary to provide means whereby the slidable on the beam and adjustable by vmeans of a nutturning on a fine pitch screw.

To obtain definite and precise settings of the instrument I preferably employ gauge blocks each representing a rack tooth of any particular pitch.

The invention Wlll be further described with reference to the accompanying drawin 's wherein Fig. 1 is a front elevation of the instrument.

Fig. 3. corresponds to Fig. 1 excepting that a gauge block is shown inpositiorj between the jaws of the instrument. i

.block.

Fig. 6 shows the instrument a gear wheel tooth.

' Fig. 7 corresponds to Fig. 3 except that the jaws are set to measure teeth of a smaller size than those gauge block.

In Figs. 1 and a. The jaw' a is shown rigidly attached to the beam 6 and the jaw a 'is slid. ably attached to the beam: aThe dial test indicator 0 is mounted on the holder 03 which is slidably mounted in the slot formed in the beam 6. The plunger e'of the d al test indicator is arranged to pass through the holder d in'a manner that its'contact point is placed between the inside faces of applied to corresponding to the and 2 the jaws are shown at a This angle is madeltocorrespond to the pressure angle of the 'geartooth to be measured. As nearly all gears are made to the standard pressure angle of, 14 9 the pro vision of means for adjusting this angle is consldered unnecessary. For. other pressure angles instruments with jaws of a corresponding angle mayv be used. Attached to jaw a is a screw which'passes through the adjustably mounted forked holder 7.

The nut h is mounted between the forked projections on the holder 9 in a manner that it may be used to make minute adjustments of the slidably mounted jaw ah j and y are looking nuts, the former forlockingthe slidably mounted jaw a and the latter for locking the holder 9. The knurled nut is serves to lock the dial test indicator holder in'a suitable position on the beam In Figs. 4; and 5 is'shown a master gauge block. This gau e block may represent a rack toothof are involute system. It may be of any desired pitch orthickness, but the angle B should correspond to the angle of the jaws a, and a On one endof the gauge block is engraved the pitch line m and also the working depth linen.

It is well-known that in the involute system oftooth gearin the theoretical rack tooth has straight sides and that any gear wheel, irrespective of the number of teeth,-.

will gearcorrectly with a rack ofthe same pitch and pressure angle- The instrument forming the subject matter of this invention is based on this principle. Fig 3 shows the instrument applied to a gauge block which, as already ex lained, represents a rack tooth. Fig. 6 s owe the instrument applied to a wheel tooth which corresponds in pitch and pressure angle to the gauge block. In applying the instrument as already described with reference to Figs. 3 and 6 the instrument is used as a comparator. Its action depends on the use of the master gauge block in conjunction with the test indicator and the jaws and other essential parts of the instrument, thus providing means of precisely comparing gear wheel teeth with a gauge block; According to this method of applying the instrument a gauge block will be required for each different size tooth to be measured, but a further method, yet to be described, can be used whereby one gauge block only is required for a range of pitches or tooth sizes.

In a series of gauge blocks made in accordance with this invention the angles are the same and therefore the only essential diderence is the width at the top where the plunger of the test indicator makes contact. By setting the jaws of the instrument as shown in Fig. 3 and adjusting'the dial of.

the test indicator to read zero a definite and known width apart of the jaws is obtained providing the width of the master block is known. Providing means are available for measuring the further adjustment of the jaws the instrument may be set to measure other sizes of teeth. The dial indicator it self maybe used to measure the relative movement of the jaws. By adjusting the slidable jaw by the means: provided, and as already described, andat the same. time holding a master gauge block in position between the jaws, the amount of movement of one jaw relative to the other will be registered by reason of the action of the gauge block on the inclined faces of the jaws in conjunction with the action of the top of the gauge block in contact with the plunger of the instrument. The movement of the plunger of the instrument will have relation to the movement of the jaws as set forth by the following equation:

Movement of plunger =movement of jaw cot. B i

Therefore, any particular size of gauge block may be used for measuring a variety of sizes of teeth. The range of sizes which maybe measured by anyparticular block will depend upon the range of movement of comprising in combination a beam, a fixed aw on the beam, a movable jaw slidably ured, means for 'movin towards oraway from t e fixed jaw,.and a plunger opei 'ated test indicator lon 'tu'di nally adjustable on the beam whereby 1t may the test indicator lunger and the particular size of the gauge 1001: used. Fig. 3 represents a master gauge block in position between the jaws of the instrument and the instrument so adjusted that it is suitable for measuring a pitch corresponding to the gauge block. Fig. 7 shows the same master gauge block in position and the: instrument so adjusted that it will measure a smaller pitchs I do not bind myself to the details of con struction shown in'the drawings. Various modifications may be made without departing from the scope and spirit of my invention. For instance, in place of the dial test indicator shown in the drawings any other suitable type of testing or measuring instrument having an amplifying mechanism may tion adapted to carry the wheel to be tested.

Having thus described the naturev of the said invention and the best means I know of carryingthe same into practical efiect, I claim I 1. A gear tooth measuring instrument mounted on the beam, said jaws'having work engaging faces inclined to one another at an angle corresponding to the pressure angle of a gear tooth to be measured, said faces arranged to have tangential bearing respectively on opposite sides of a toothto be measured, means for moving the movable jaw minute distances lengthwise of the beam, means for clamping the movable jaw in any adjusted position, a plunger-operated test indicator mounted on the beam, and means for adjustably securing the indicator tothe beam in position relativel to the jaws when adjusted to dispose the p unger between the aws. 2. A gear tooth measuring instrument comprising a beam, fixed and movable jaws carried thereby having their opposed faces inclined at an angle corresponding to the pressure angle'of a gear tooth to be ,measthe movable jaw be disposed between the jaws when the latter are in operative position. v,

lin testimony whereof I have signed my name to this specification.

' WELLEAM EDW'XN SYKES. 

